One of pressure sensor modules suitable for use for a gas pressure detecting unit or the like which have been conventionally known in the art is so constructed that a pressure sensing element, a circuit board, a part of a connector and the like are arranged in a housing. The pressure sensing element is a sensor element constituted by a sensor element of the capacitance type. The pressure sensing element is so constructed that a pair of insulating substrates (a diaphragm substrate and a base substrate) such as ceramic plates of which at least one is movable or flexible in response to a pressure applied thereto are provided on surfaces thereof opposite to each other with facing electrodes, respectively, resulting in a variation in pressure being detected based or depending on a variation in capacity between the facing electrodes. The connector is constructed in such a manner that terminal members made of metal are fixed on a connector body formed of an insulating material consisting of synthetic resin. Such a conventional pressure sensor module is disclosed in Japanese Patent Application Laid-Open Publication No. 19527/1988 or U.S. Pat. No. 4,774,626. In the pressure sensor module disclosed, a flange is integrally formed on a lower end of a connector body. The flange of the connector body is received in a housing while being laminatedly supported on a pressure sensing element through a support ring and then is subject to curling (caulking), resulting in being wrapped in an end of the housing. Unfortunately, an insulating material for the flange is reduced in pressure resisting strength or pressure resistance. Thus, mounting of the connector by wrapping the flange in the end of the housing by caulking possibly causes detachment of the connector from the housing or breakage of the connector, when force of increased magnitude is continuously applied to the flange through the pressure sensing element and support ring. In view of the fact, Japanese Patent Application Laid-Open Publication No. 190731/1990 or U.S. Pat. No. 4,888,662 proposes a pressure sensor module constructed so as to solve such a problem. More particularly, in the pressure sensor module proposed, a support member (a support substrate) made of metal is arranged between a pressure sensing element and a connector to mechanically insulate both from each other for the purpose of preventing force from being applied to a connector body through the pressure sensing element.
However, such arrangement of the support substrate made of metal between the pressure sensing element and the connector causes a thickness or height of the whole pressure sensor module to be increased by an amount corresponding to a thickness of the support substrate, to thereby fail to compact the pressure sensor module. Also, the support substrate made of metal causes static electricity charged on an outside of the pressure sensor module through the support substrate to enter a circuit board through the support substrate, leading to generation of noise and, in the worst case, breakage of electronic elements. In particular, the latter techniques, when the support substrate is deteriorated in working or processing accuracy and more particularly a contact surface of the support substrate with the pressure sensing element is worked or processed in deteriorated accuracy, cause spot contact or partial contact to occur between the support substrate and the pressure sensing element, leading to local application of force to the pressure sensing element, resulting in the pressure sensing element being possibly broken.
Accordingly, it is an object of the present invention to provide a pressure sensor module which is capable of restraining force of large magnitude from being applied to a connector and reducing a height or thickness of the module, to thereby accomplish compaction thereof.
It is another object of the present invention to provide a pressure sensor module which is capable of restraining both application of force of large magnitude to a connector and intrusion of static electricity into a circuit board.
It is a further object of the present invention to provide a pressure sensor module which is capable of restraining application of force of large magnitude to a connector and preventing breakage of a pressure sensing element due to local application of force to the pressure sensing element.
It is still another object of the present invention to provide a pressure sensor module which is capable of minimizing damage to a surface of a coupling or connection section of a housing due to curling of the connection section.
It is yet another object of the present invention to provide a pressure sensor module which is capable of preventing occurrence of cracks in a flange of a connector body.
It is a still further object of the present invention to provide a pressure sensor module which is capable of readily preventing intrusion of water thereinto through a gap between a connection section of a housing and a connector body.
It is a yet further object of the present invention to provide a pressure sensor module which is capable of exhibiting increased reliability as compared with the prior art.